Heat Exchanger

ABSTRACT

The invention relates to a heat exchanger ( 1 ) with flow channels ( 3 ), which can be flowed through from a common first inlet to a common first outlet by a first fluid, comprising a housing ( 2 ), which accommodates the flow channels ( 3 ) and which can be flowed through by a second fluid from a second inlet area to a second outlet area. The flow channels ( 3 ) have a flat cross-section as well as longitudinal sides ( 3   a ) and are flow-connected to one another. The invention provides that the longitudinal sides ( 3   a ) of the flow channels ( 3 ) are integrally connected to the housing ( 2 ), particularly by soldering.

The invention relates to a heat exchanger as claimed in theprecharacterizing clause of patent claim 1, known from DE 100 60 102 A1.

US 2003/0010479 A1 discloses a heat exchanger which can be used as anexhaust-gas cooler in an exhaust-gas feedback system. Exhaust-gas tubesare arranged in a housing through which liquid coolant in the coolingcircuit of an internal combustion engine flows and are held at the endin tube bases which are themselves connected to the housing. The exhaustgas is supplied to the exhaust-gas cooler via a diffusor, then flowsthrough the exhaust-gas tubes around which the coolant flows, andemerges from the cooler via an exhaust-gas connecting stub. All theparts of the exhaust-gas cooler are soldered to one another. This designwith tube bases in which the tube ends are held has the disadvantagethat the tubes are fixed in the tube bases during the soldering processand therefore cannot move towards one another during soldering andduring melting of the solder layer which, inter alia, also has adisadvantageous effect on the soldering of the turbulence inserts to thetube inner walls. This disadvantage is avoided by systems without tubebases, as shown by the following example:

DE 100 60 102 A1 discloses a heat exchanger which can likewise be usedas an exhaust-gas cooler in an exhaust-gas feedback system. In thiscase, fed-back exhaust gas is cooled by coolant which is taken from thecooling circuit of the internal combustion engine for the motor vehicle.The known exhaust-gas cooler has a housing which is essentially in twoparts and in which a heat sink is arranged, through whose primary sidecoolant can flow and which comprises a multiplicity of flat small tubesand through whose secondary side exhaust gas flows. In this case, theexhaust gas is passed through the housing in a relatively straight line,that is to say without any significant direction changes. The coolant isinput and output at right angles to the flat small tubes, thus resultingin 90° direction changes in each case. In order to improve the heattransfer between the exhaust gas and the coolant, so-called turbulencesheets are arranged between the flat small tubes. The entire exhaust-gascooler comprising the housing, small tubes and turbulence sheets isproduced by “integral soldering”.

The application subject matter of DE 100 60 102 A1 results from theprior art as shown in FIG. 9, which relates to an exhaust-gas heatexchanger without a housing, with flat exhaust-gas tubes being formedfrom plates whose fold has angled raised rim strips on the longitudinalfaces, which are soldered to adjacent rim strips to form a housing wall.This has the disadvantage that there are a multiplicity of solderpoints, each of which is intrinsically subject to the risk of leakage,and thus of exhaust-gas leakage. The application subject matter of DE100 60 102 A1 has the disadvantage that the exhaust-gas flow actsdirectly on the housing walls which are therefore heated to atemperature which is incompatible with the area surrounding the built-inexhaust-gas cooler, for example the engine bay of a motor vehicle.

One object of the present invention is to design a heat exchanger of thetype mentioned in the introduction on the one hand to be suitable forjoining techniques, in particular soldering, welding, adhesive bondingetc., and on the other hand to keep its external temperature low whenusing hot media to be cooled.

This object is achieved by the features of patent claim 1.

The invention provides that the flow channels, which are preferably inthe form of plate pairs, are preferably integrally connected on thelongitudinal faces to the walls of the housing, that is to say bysoldering, welding, adhesive bonding etc. The plate pairs are placed inlayers on top of one another to form a pack, and are connected to oneanother for flow purposes by means of lateral channels. When the flowpasses through these lateral channels, this results in a comparativelyhigh pressure loss, on the one hand as a result of the direction of thefluid being changed from the lateral channel into the channels which areenclosed by the plate pairs, but in particular because the lateralchannels normally have sharp end edges between the plate pairs whichlead to severe vortexing of the fluid, and thus to high pressure losses.A first fluid, preferably a liquid coolant, therefore flows through theplate pairs, with this first fluid being less critical in terms of thepressure losses in the cooler. At the end, a second fluid, in particulara hot medium to be cooled, flows into and through the pack of the platepairs, thus resulting in the flow passing in a relatively straight linethrough the plate pack, that is to say without any significant directionchanges. This results in little pressure loss for the second, preferablygaseous, fluid. Turbulence-generating devices are provided between theplates as appropriate for the heat-transfer conditions. The heatexchanger according to the invention is preferably soldered, welded,adhesively bonded etc. in one process. Those parts which are to besoldered, welded or adhesively bonded are in this case arranged flexiblywith respect to one another, that is to say such that they can move withrespect to one another, and can therefore in particular move relative toone another when the soldered layers are melted during the solderingprocess, thus resulting in minimal solder gaps and good soldering. Theplate pairs can advantageously be prefolded in a method step whichprecedes the joining process, in particular the soldering process,welding process, adhesive-bonding process etc., and/or can be crimped,that is to say the plate pair comprising two plates and if appropriateincluding any turbulence inserts to be provided can be prefabricated insuch a way that the plate pair is fixed by means of lugs which areformed from one plate and surround the rim of the other plate, so thatthe two plate sheets of the plate pair can no longer slide with respectto one another, can no longer be moved with respect to one another, orcan no longer gape open during the actual soldering process, thusensuring that the plate pair is soldered such that they are sealed.Crimped plates can prevent, for example, relative movements between thehousing and the plate pair resting on it along it as a result of thecomponents being heated at different rates and the solder layers meltingleading to inadequate soldering of the plate pair. This also simplifiestolerance matching between the longitudinal face of the plate pair andthe housing since, essentially, all that is necessary is to ensure thatthe crimped plate pair rest on the housing during the soldering process,without any need to consider possible movements of the two plates withrespect to one another. This ensures that the integral connection of theflow channels and plate pairs results in thermal conduction between thefirst flow, the cooling medium, and the housing walls. Because of thethermal coupling, the housing wall also contributes to the heattransfer, and the linking of the plate pairs makes it possible toconsiderably increase the heat-transfer area for the second fluid,depending on the heat-exchanger geometry and the configuration of theturbulence generators: from about 2% to more than 10% when oneturbulence sheet is provided in the channel for the second fluid, andeven up to more than 25% when turbulence generators (for example avortex body that is stamped into the plate) are used in the channel ofthe second fluid. This results in an increase in the heat-exchangerperformance, which may be considerable. Furthermore, when using a hotmedium to be cooled, the housing wall can be adequately cooled and canbe kept at a relatively low temperature level. However, particularly inthe case of exhaust-gas coolers and boost-air coolers, adequate coolingof the housing is often absolutely essential in many otherheat-exchanger applications since, otherwise, very large thermalstresses will occur at the connecting points between the housing and theplate pairs, caused by the large temperature differences and thecorrespondingly different thermal expansions of the housing carryingexhaust gas, and the cooled plate pairs. A further major advantage oflinking the longitudinal faces of the plate pairs to the housing is theconsiderable increase in the pressure resistance of the heat exchangerwith respect to the second fluid, since the plates represent a tie rodbetween the two housing sides, opposing the internal pressure. Theproposed heat-exchanger concept is therefore particularly suitable formedia in which the pressure-loss requirements for the second fluid arehighly restrictive, the second fluid is very hot, or the pressures ofthe second fluid are high, or combinations of these requirements.

In one development of the invention, the flow channels are integrallyconnected to the housing essentially over the entire length of thelongitudinal faces. The integral connection is produced in particular bysoldering, welding, adhesive bonding etc., but in principle it is alsopossible to use any other type of connection, such as an interlockingconnection or a combination of an integral connection and aninterlocking connection.

In one development of the invention, the flow channels are in the formof plate pairs. The plate pairs form channels for a second fluid to passthrough. There is a connection between the plate pairs and the housing,so that the second fluid has access to the housing and to the housingwall, and therefore, for example, cools or heats the housing wall andthe housing.

In one development of the invention the flow channels and/or thechannels for the second fluid to pass through are essentially held intheir entirety by the housing, so that the heat transfer between thefirst and the second fluid takes place essentially entirely in theinterior of a housing which can be closed by a cover, with heat likewisebeing transferred between the second fluid and the housing and/or thecover, as well as between the first fluid and the housing and/or thehousing cover.

In one development of the invention, at least one flow channel for afluid, in particular the first fluid, is formed between the cover of anadjacent plate, in particular a lower plate, thus saving an upper plate,with the cover being additionally cooled at the same time. Since thecover is integrally connected to the housing, for example by soldering,welding, adhesive bonding etc., and/or is connected by means of aninterlock such as forming, heat is transferred between the cover and thehousing, and vice versa, so that the housing is also cooled.

In another development of the invention, at least one flow channel forthe first fluid is formed between the base section of the housing or thehousing shell and an adjacent plate, in particular the upper plate, andbetween the base section of the housing shell, in this way likewisesaving one plate, in particular a lower plate. In particular, the firstfluid then cools the housing and the housing shell. Furthermore,however, it is also possible to connect the upper plate to a lowerplate, in particular integrally, thus forming a plate pair which isintegrally connected, in particular by soldering, welding, adhesivebonding etc., via at least one plate to the housing shell in the basearea, in particular to the lower plate adjacent to the base area.

In one development of the invention, the lower plate and upper platewhich in each case form a plate pair are connected to one another bymeans of a fold that is formed at the rim, with the plates thereforebeing connected to one another in an interlocking manner, in particularby bending. In this case, at least one plate, in particular the lowerplate, clasps the other plate, in particular the upper plate, thusresulting in the plates being hooked to one another with tolerancecompensation at the same time being possible in the stacking directionof the plates and of the plate pairs, so that, during the joiningprocess, for example soldering, welding, adhesive bonding etc., by meansof which the integral connection is produced, it is possible tocompensate for any openings or gaps between the plates, so that thejoining process can be carried out successfully by means of a reliableprocess, thus resulting in a complete, integral connection between theplates, in particular the upper plate and the lower plate, as well asbetween adjacent plate pairs and between adjacent upper plates and lowerplates.

In one development of the invention, an inlet flow channel and/or atleast one outlet flow channel run/runs transversely through the platepairs, and in this case the inlet flow channel and/or the outlet flowchannel may run through the plate pairs, at an angle of 0° to 360°, or−360°, to the stacking direction of the plates and/or to thelongitudinal direction of the plates, in particular at an angle of −50°to +500 to the stacking direction, and particularly advantageously at anangle of 0° to the stacking direction, that is to say the inlet flowchannel and/or the outlet flow channel run essentially parallel to thestacking direction. The angles of the outlet flow channel and of theinlet flow channel to the stacking direction and/or to the longitudinaldirection may in this case differ, and may assume values between 0° and360° or −360°.

In one development of the invention, the plate pairs have at least onedepression or at least one protrusion. The depression or the protrusionis in this case incorporated in at least one plate of a plate pair ineach case, preferably by forming techniques such as bending, stamping,etc., or by primary forming, etc.

In one development of the invention, the protrusion or the depression onor in a plate pair extends to an adjacent plate pair, with the platesand the plate pairs touching, and in particular being integrallyconnected to one another by soldering, welding, adhesive bonding etc.Furthermore, an interlocking connection and/or a combination of aninterlocking connection and an integral connection are also possible, inthe same way as other connections.

In one development of the invention, the protrusion or the depression isincorporated in the upper plate, in particular by forming or primaryforming, in the same way as an upper plate annular surface which touchesa lower plate annular surface, which is incorporated by forming orprimary forming, of the lower plate of an adjacent plate pair and, inparticular, is integrally connected to the lower plate annular surfaceby soldering, welding, adhesive bonding, etc. and/or by means of aninterlock, such as hooking.

In another development of the invention, another protrusion isincorporated in the lower plate, in particular by forming and/or primaryforming, in the same way as a lower plate annular surface which touchesan upper plate annular surface of the upper plate of an adjacent platepair and in particular is integrally connected to the upper plateannular surface by soldering, welding, adhesive bonding etc., and/or byan interlock, for example by hooking.

In one development of the invention, the flow channels are stacked. Thechannels for the second fluid to pass through can likewise also bestacked. In one development, the plates are stacked such that one plateis stacked on another adjacent plate and such that, in particular, anupper plate is placed on a lower plate and the upper plate has a furtherlower plate placed on it, on which, in turn, a further upper plate isplaced, so that adjacent plate pairs are stacked one on top of theother. The stack formed by the plates, or the stack of plate pairs, isitself inserted into the housing shell, which is closed by a cover. Thecover is in this case placed on the housing such that it is placed onthe housing in a stacking direction and is connected to it by aninterlock, in particular by soldering, welding, adhesive bonding etc.,and/or integrally, in particular by forming, hooking, etc., thusallowing tolerances to be compensated for in the stacking direction ofthe flow channels and of the channels for the second fluid to passthrough, during the joining process, in particular the soldering,welding or adhesive bonding.

In one development of the invention, the plates in a plate pair haveplate rim surfaces such that the upper plate of a plate pair has anupper plate rim surface, and the adjacent lower plate has a lower platerim surface, with the upper plate rim surface corresponding to the lowerplate rim surface and being integrally connected in particular bysoldering, welding, adhesive bonding etc. The upper plate rim surfaceruns in the longitudinal direction of the plate essentially parallel tothe lower plate rim surface, and the upper plate rim surface likewiseruns in the same way in the direction of the plate width which, inparticular, is formed essentially at right angles to the longitudinaldirection of the plate and essentially at right angles to the stackingdirection of the plates, as well as essentially parallel to the lowerplate rim surface. An abutment between the lower plate rim surface andthe upper plate rim surface is formed in those sections of the upperplate rim surface and of the lower plate rim surface in which thelongitudinal face of the plate merges into the plate width in thestacking direction, such that the abutment of a plate rim surface in thelongitudinal direction is essentially in the form of a quarter cylinder,and such that the quarter cylinders of the lower plate and upper plateessentially touch like two concentric quarter cylinders that are pushedone inside the other, and are integrally connected, in particular bysoldering, welding, adhesive bonding etc.

In one development of the invention, the longitudinal faces of two platepairs which form a flow channel clasp one another at least in places, inparticular over the entire plate length, such that the longitudinal facewhich touches the housing clasps the longitudinal face of an adjacentplate, in particular the other plate of the respective plate pair, andsuch that the two plates are in this way crimped to one another.

In one development of the invention, broader faces of two plate pairswhich form a flow channel clasp one another at least in places, inparticular over the entire plate width. In this way, the two plates, inparticular the upper plate and the lower plate of a plate pair, arecrimped to one another.

In one development of the invention, the plate pairs haveturbulence-generating devices, in particular turbulence inserts orstamped-in structure elements. In this case, the turbulence inserts maybe designed such that they are sheets with stamped-out areas and/ormeshes composed of wire. The content of the unpublishedDE102004037391.4, DE19718064B4 and DE19709601C2 is hereby expresslydisclosed.

In one development of the invention, the protrusions are conical and arein the form of truncated cones which are produced from a plate,preferably by forming techniques such as stamping or primary forming.That side surface of the truncated cone which has the smaller of the twodiameters is in the form of an annular surface, which touches theadjacent plate, preferably the lower plate of the next plate pair, andin particular is integrally connected to it by soldering, welding,adhesive bonding etc.

In one development of the invention, the protrusions are streamlined, inparticular with an elongated, elliptical or round cross section.

In one development of the invention, turbulence-generating devices areincorporated between flow channels and/or in the channels for the secondfluid to pass through. The contents of the unpublished DE102004037391.4,DE19718064B4 and DE19709601C2 are expressly disclosed in this context.

In one development of the invention, the folded connections areconnected to the housing, in particular to the inner surface of thehousing, with the connection being produced in particular integrally bysoldering, welding, adhesive bonding etc.

In one development of the invention, the inlet area of the housing isarranged in front of the plate pairs in the flow direction of the secondfluid.

In one development of the invention, the outlet area of the housing isarranged behind the plate pairs in the flow direction of the secondfluid.

In one development of the invention, the second fluid can flow aroundthe plate pairs essentially parallel to their longitudinal faces.

In one development of the invention, the fold on the longitudinal faceis formed by rims of an upper plate and lower plate in the same sensethat are bent. The fold on the longitudinal face furthermore forms acontact surface for the housing.

In one development of the invention, the fold on the longitudinal faceis formed by rims of an upper plate and lower plate in opposite sensesthat are bent. The fold on the longitudinal face furthermore forms acontact surface for the housing.

In one development of the invention, the plate pairs have side channelsfor the first fluid on the longitudinal face in the area of the housingwalls.

In this case, the side channels are in the form of an extension of theflow cross section of the plate pairs. The extension has a channelheight which corresponds essentially to the distance between the platepairs.

In one development of the invention, the plate pairs have a flow crosssection with a channel width b, and the housing walls are separated by adistance w, where b<w and material bridges are arranged between the flowcross sections and the housing wall, and are in particular formed from alower plate and/or an upper plate.

In one development of the invention, the housing is formed in at leasttwo parts, and has a housing shell as well as a cover.

In one development of the invention, the inlet area of the housing hasan inlet connecting stub which is arranged in the housing shell or inthe cover. Moreover the outlet area of the housing has an outletconnecting stub which is arranged in the housing shell or in the cover.

In one development of the invention, the housing has an inlet connectingstub and an outlet connecting stub for the first fluid, with the inletand outlet connecting stubs for the first fluid being arranged in thecover or in the housing shell, and having longitudinal axes which are atan angle to the plate pairs.

In one development of the invention, the heater exchanger has a bypass.A bypass channel for the second fluid is arranged within the housing andparallel to the plate pairs. The mass flow of the second fluid is forthis purpose split into at least two mass flow elements, in particularby means of a separating wall, with at least one first mass flow elementof the second fluid flowing through the channels for the second fluid topass through, and with at least one second mass flow element of thesecond fluid flowing through the bypass.

In one development of the invention, the plate pairs form a pack throughwhich the second fluid flows on two paths. A separating wall is arrangedin the inlet area for the second fluid and/or in the outlet area for thesecond fluid. In this case, in particular, the separating wall isarranged such that it can rotate, so as to make it possible to set anangle of between 0° and 360° between the flow direction of the secondfluid and a longitudinal face of the separating wall.

In one development of the invention, the heat exchanger contains atleast one non-return valve, which is preferably integrated in thehousing and is located in the outlet area.

In one development of the invention, the bypass channel is arrangedabove or below the plate pairs in the heat exchanger.

In one development of the invention, the bypass channel is in the formof a bypass tube which can be inserted into the housing. The bypass tubeis in this case thermally insulated from the flow channels (3) and/orfrom the channels for the second fluid to pass through, in particular insuch a way that as little heat as possible is transferred between thesecond mass flow element, which flows through the bypass channel and/orthe bypass tube, and the first mass flow element which, in particular,is cooled.

In one development of the invention, the bypass tube is essentiallyarranged at a distance from the flow channels and/or from the channelsfor the second fluid to pass through. The separation is preferablyprovided by protrusions or stamped-out areas which are incorporated inthe bypass tube and/or in the flow channels and/or the channels for thesecond fluid to pass through.

In one development of the invention, the bypass tube comprises at leastone partial element which is preferably in the form of an open profileand particularly advantageously is in the form of a U-profile orhalf-tube.

In one development of the invention, the bypass tube comprises two tubehalves, which are preferably integrally connected to one another bysoldering, welding, adhesive bonding, etc.

In one development of the invention, the bypass tube has at least onelongitudinal separating wall.

In one development of the invention, at least one bypass flap isintegrated in the inlet or outlet area of the housing. The bypass flapis variable and may assume an angle from 0° to 360°, thus splitting themass flow of the second fluid into the first mass flow element and thesecond mass flow element. The first mass flow element flows through thechannels for the second fluid to pass through and, in particular, iscooled in the process. The second mass flow element flows, in particularwithout being cooled, through the bypass. The bypass valve can be usedto adjust and/or to provide open-loop and/or closed-loop control for thefirst mass flow element of the second fluid through the channels for thesecond fluid to pass through. The second mass flow element of the secondfluid through the bypass is a function of the set first mass flowelement, and can therefore likewise be subjected to open-loop and/orclosed-loop control.

In one development of the heat exchanger, the inlet area has twoseparate inlet connecting stubs as well as one separating wall.

In one development of the invention, the plate pairs form a pack throughwhich the second fluid flows on two paths. An inlet chamber and anoutlet chamber are arranged on one side of the plate pack. A deflectionchamber for the second fluid is arranged on the other side of the platepack.

In one development of the invention, the bypass is integrated in thehousing. In particular, the bypass is formed integrally with thehousing.

In one development of the invention, the bypass is integrated in thecover. In particular, the bypass is formed integrally with the cover.

A heat exchanger as claimed in one of the preceding claims,characterized in that the flap is arranged in the inlet area or in theoutlet area.

In one development of the invention, the heat exchanger has at least onebypass valve which provides open-loop and/or closed-loop control for thevolume flow and/or mass flow in particular of the second fluid throughthe bypass. The bypass valve is preferably integrated in the housingand, in particular, is formed integrally with it. The bypass valve isarranged in the inlet area and/or in the outlet area.

In one development of the invention, the bypass valve is a combinationvalve, which is referred to in the following text as a heat-exchangervalve device. The heat-exchanger valve device is characterized in thatthe valve plate can be rotated between a first open position, in whichthe bypass output is closed and the heat-exchanger output is open, and asecond open position, in which the bypass output is open and theheat-exchanger output is closed. The rotating valve plate makes itpossible to ensure adequate sealing, even at high pressures.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the rotating valve plate has an openingthrough which fluid can pass, which, by at least partial rotation, canbe made to coincide with one of two further openings through which fluidcan pass, and which are provided in a valve plate which is fixedrelative to the valve housing. The three openings through which fluidcan pass are preferably designed to be coincident with one another.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that one of the openings through which fluidcan pass in the fixed valve plate is connected to the heat-exchangeroutput, and the other opening through which fluid can pass is connectedto the bypass output. Depending on the extent to which the openingsthrough which fluid can pass in the valve plates cover one another, moreor less or even no fluid is passed to the bypass output and/or to theheat-exchanger output.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the fixed valve plate has a depressionin which the rotating valve plate is guided. This results in theadvantage that there is no need for the valve plate to be guided on thevalve housing.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the fixed valve plate has an externalthread by means of which the fixed valve plate can be screwed into acomplementary internal thread in the valve housing. This makes it easierto fit the fixed valve plate.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that an actuator rod projects from therotating valve plate. The actuator rod, which is preferably passed outof the valve housing, makes it easy to operate the rotating valve plate.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the valve plates are at least partiallyformed from ceramic. Stainless steel can also be used instead ofceramic.

One preferred exemplary embodiment of the heat-exchanger valve device ischaracterized in that the valve slide can be moved backwards andforwards between a first extreme position, in which the bypass output isclosed and the heat-exchanger output is open, and a second extremeposition, in which the bypass output is open and the heat-exchangeroutput is closed. The valve slide makes it possible to ensure adequatesealing even at high pressures.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the valve slide is formed partially fromceramic. Stainless steel can also be used instead of ceramic.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the valve housing is formed partiallyfrom ceramic. The contact surface for the valve slide is preferablyformed from ceramic.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the valve slide is equipped with asealing element for the input. The input is preferably equipped with asealing seat for the sealing element.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the sealing element has a sealingsurface facing the input, in the form of a spherical section. The use ofa spherical section with a large diameter makes it easier for the valveslide to move.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the sealing element is guided such thatit can move backwards and forwards on the valve slide. This makes iteasier to close the input by means of the sealing element, which is alsoreferred to as a closing element.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the sealing element is prestressedagainst the input by a spring device. This allows the input to be closedto form a seal.

A further preferred exemplary embodiment of the heat-exchanger valvedevice is characterized in that the valve slide has a pressureequalizing channel. This makes it easier to move the valve slide in thevalve housing.

In one development of the invention, the integrated bypass has aseparating wall which can pivot and by means of which the inletconnecting stub and the outlet connecting stub can be short-circuited.

In one development of the invention, the first fluid is a liquidcoolant, in particular the coolant from the cooling circuit of aninternal combustion engine for a motor vehicle, and the second fluid isfed-back exhaust gas from the internal combustion engine.

In one development of the invention, the first fluid is air, and thesecond fluid is fed-back exhaust gas from an internal combustion enginefor a motor vehicle.

In one development of the invention, the plate pack is preceded by anoxidation catalytic converter, for example as disclosed in theunpublished DE 10 2005 014 295.8. The entire content of the unpublishedDE 10 2005 014 295.8 is hereby disclosed expressly.

In one development of the invention, the first fluid is a liquidcoolant, in particular the coolant in the cooling circuit of an internalcombustion engine for a motor vehicle, and the second fluid is boost airwhich can be supplied to the internal combustion engine.

In one development of the invention, the first fluid is air and thesecond fluid is boost air which can be supplied to an internalcombustion engine for a motor vehicle.

In one development of the invention, the heat exchanger is used as anexhaust-gas cooler in an exhaust-gas feedback system for an internalcombustion engine for a motor vehicle or as a heater for heating theinterior of a motor vehicle, in which case the heat transferred from thesecond fluid to the first fluid is used to heat the interior of thepassenger compartment of a vehicle.

In one development of the invention, the heat exchanger is used as anoil cooler for cooling engine oil for an internal combustion engine orgearbox oil for a motor vehicle by means of a liquid coolant, preferablythe coolant in the cooling circuit of the internal combustion engine.

In one development of the invention, the heat exchanger is used as acoolant condenser in the coolant circuit of a climate-control system formotor vehicles.

In one development of the invention, the heat exchanger is used as acoolant exhaust-gas cooler in the coolant circuit of a climate-controlsystem for motor vehicles.

In one development of the invention, the heat exchanger is used as acoolant vaporizer in the coolant circuit of a climate-control system formotor vehicles.

Further advantageous refinements of the invention are specified in thedependent claims.

One particularly advantageous refinement of the invention is representedby concepts in which the rims of both plates of the plate pair areformed circumferentially and without any interruptions such that theymake flat contact with one another everywhere (FIGS. 1, 2 c, 3 a, 3 b, 3c). This can also be described by the two plates being formed on thecircumferential outer rim everywhere along their contact line such thatthey are at an angle of 0° with respect to one another on the plane atright angles to this contact line, with this angle being greater than10° only exceptionally. In this case, the two plates can rest flat onone another, for example, on their contact line so that, in the sectionat right angles to the contact line, the two plates run largely parallelto one another over a certain distance. One or both plates may also, forexample, be formed to be curved with respect to one another in the areaof the contact line, so that, in the section at right angles to thecontact line, the contact of a straight line with a circle segment or,if both are designed to be curved, the point contact of two circlesegments results, with just one contact point but no contact line.Furthermore, for example, the rims of the two plates can also bedesigned such that one has a concave shape and the other has a convexshape, with two circle segments on the plane at right angles to thecontact line, which circle segments touch either only as a point orpoints or over a certain circle-arc segment. All of these examples havean angle of exactly 0° with respect to one another on thecircumferential contact line. According to the invention, the embodimentof the plate pairs which is described as being straight may therefore bedeigned to be very flexible, because the housing results in the flowchannel for the second fluid being sealed everywhere on the longitudinalfaces so that no soldering to adjacent plate rims is required at theouter rims of the plate pair. FIG. 2 c represents a good compromisebetween process-optimized design of the plate pair, allowingcircumferential flat contact with a small contact angle between the twoplates, and excellent thermal connection of the housing to the channelfor the first fluid.

According to a further advantageous refinement of the invention, thehousing is formed in at least two parts, that is to say for example froma first housing part in the form of a trough, a housing shell, and asecond part in the form of a cover. The two parts can be placed oneinside the other and can easily be joined to one another, in particularby soldering, welding, adhesive bonding etc. A housing concept such asthis also results in an optimum joining process, in particular asoldering process, welding process, adhesive-bonding process, etc.,between the stacked plate pairs, when the housing parts are likewisepushed one inside the other, or placed one on top of the other, in thestacking direction of the plate pairs, and are joined to the housing bysoldering, welding, adhesive bonding etc. during the joining process, inparticular the soldering process, welding process, adhesive-bondingprocess etc. In one suitable embodiment, the housing parts can then alsomove towards one another to the same extent with the plate pairs sothat, for example, no gaps or solder, welding and/or adhesive bondingfaults occur as a result of the melting solder layers. Like the cover,the housing shells can advantageously be produced as formed and/orprimary-formed parts such as thermoformed or deep-drawn parts, in whichcase the housing shells may also form the inlet and outlet areas for thesecond fluid. Furthermore, inlet and outlet connecting stubs both forthe first and the second fluid can be integrally formed, for example inthe form of passages, on the housing, irrespective of whether this isthe housing shell or the housing cover. The position and shape of theconnecting stubs can be chosen as required, depending on therequirements for the heat exchanger. For example, the inlet and outletconnecting stubs for the second fluid may be located at the same coolerend or at opposite ends (see the explanatory notes relating to thisfurther below), and the inlet and outlet may be provided in any desireddirection, that is to say for example in the longitudinal direction ofthe cooler, upwards—in this case out of the cover, downwards from thehousing or at the side out of the housing.

According to a further advantageous refinement of the invention, abypass channel can be arranged parallel to the plate pack in thehousing, in which case, for example, the bypass may be in the form of atube which is inserted into the housing and is soldered to the otherparts. A bypass such as this is particularly advantageous when using theheat exchanger as an exhaust-gas cooler in an exhaust-gas feedbacksystem. Bypass arrangements such as these in conjunction withappropriate bypass flaps for control of the exhaust-gas flow through theheat exchanger or through the bypass are known per 5 e from the priorart. The design of the heat exchanger according to the invention allowsa bypass channel and a bypass flap to be integrated in the exhaust-gascooler, using simple means. The fluid flow which is carried in thebypass must also be carried separately from the fluid flow in the inletarea, which flows through the heat-exchanger channels. For this purpose,a separating plate or separating element, in the simplest form aseparating plate, can be provided in the inlet area for the secondfluid, separating the inlet area into two areas, one for the bypassfluid flow and the other for the heat-exchanger fluid flow. By way ofexample, separating elements may be clamped, welded or soldered in onehousing part or between housing parts. The separated inlet areas mayeither each have their own inlet openings in the housing or may besupplied with the fluid flows through a common inlet opening, but whichis split in two by the separating element. In the case of the commoninlet opening, of course, the two fluid flows must also be separated inthe supply line of the second fluid, or a bypass flap must be fitteddirectly to the inlet opening in a manner such that it is directlyclosed by the separating element and no unacceptable leakages can occurfrom the bypass side to the heat-exchanger side, and vice versa. Forexample, this can be achieved by flange connection or a flange-connectedmodule comprising a flap, housing and actuator. Furthermore, the bypassflap can also be integrated in the inlet area of the second fluid suchthat the gas flow is passed directly into the bypass channel or into theheat-exchanger channels, as required. In the case of an integratedbypass flap such as this as well, an additional separating element mayalso be required between the start of the bypass and the flap forsealing purposes. All the described solutions can likewise be providedwith the same functionality in the outlet area for the second fluid,that is to say a separating element and bypass flap in the describedarrangements and combinations. The statements relating to the need toseparate the fluid flows in the supply line then apply in acorresponding manner to the output line. All the solutions are alsopossible with a combination valve instead of a bypass flap, that is tosay it is also possible to completely block the second fluid, inaddition to the fluid being passed into the heat-exchanger channels orinto the bypass. For example, the described bypass flaps or valves canbe operated via an electrical actuator or via a pressure controlelement.

The heat exchanger according to the invention allows the bypass channelto be embodied in widely differing ways. In one development of theinvention, the bypass is inserted underneath the lowermost plate orabove the uppermost plate in the stacking direction of the plate pairs.It is directly adjacent to the housing. In one development of theinvention, the bypass is inserted into the housing at the side,alongside the stacked plate pairs. In one development of the invention,the bypass channel is formed integrally with the housing by impressingone or more longitudinal beads into the housing such that the bypasschannel is formed in this way and is bounded on one side by the housingwall and on the other side by the first plate of the plate stack. In onedevelopment of the invention, a bypass is formed such that anessentially U-shaped shell is placed on one housing side, and inparticular is joined to it, and in particular is soldered, welded, oradhesively bonded, etc., to it. In this case, the bypass is enclosedbetween the fitted shell and the housing wall. Furthermore, a heatexchanger according to the invention can also be combined with acompletely external bypass, that is to say a closed flow channel for thesecond fluid, which can be connected to the heat exchanger, for exampleby welding or soldering, or can be fixed with the heat exchanger incommon holders. However, an external bypass may also be routedcompletely separately from the heat exchanger.

In one development of the invention, any form of spacer may be usedbetween the plate stack and the housing wall, such as a corrugated plateor a ribbed plate. Furthermore, it is possible to use permeablestructures such as wire meshes, porous materials or the like. A shellextending in the longitudinal direction may also be particularlyadvantageous, having a U-profile and being open towards a housing wall.It supports the plate stack by means of the closed side.

In one development of the invention, the structures which form thechannel project in the longitudinal direction beyond the heat-exchangerchannels formed by the stacked plates into the inlet and/or outlet areaof the second fluid. This means there is no need for a separatingelement between the bypass fluid flow and the heat-exchanger fluid flow.In one development of the invention, the integrated bypass flap isdesigned such that no additional separating element is required for thebypass channel.

The bypass channel is intended to allow the second fluid to bypass theheat-exchanger channels without any major energy transfer from or to thefirst fluid, and it should therefore be thermally decoupled as well aspossible from the first fluid. The decoupling can be achieved, forexample, by a stud or bead support for the bypass channel against thehousing wall and/or against the plate stack. The studs or beads may inthis case be stamped out both from a structure which forms the bypasschannel, for example a tube, and/or from the housing wall or theadjacent first plate in the plate stack. Additional insulation can alsobe inserted between the bypass channel and adjacent structures as aninsulating element with poor thermal conductivity (a good insulatingeffect). The insulating effect is achieved by insulating materialsand/or by shaping, in particular by means of a ribbed structure.

In one development of the invention, the bypass channel has doublewalls, in particular with a thicker, load-bearing outer wall and athinner, inner wall. The two walls are designed such that the outer wallis subject to less thermal stresses than the inner wall.

A further refinement of the invention provides for the flow to passthrough the heat exchanger on two or more paths, that is to say for thesecond fluid to be split into flow elements which are each passedthrough some of the heat-exchanger channels parallel or in oppositedirections. The same requirements for separating plates and inlet/outletopenings may be used to separate the flow elements as those alreadydescribed in conjunction with integration of the bypass tube.

In one development of the invention, the exhaust-gas flow elements areeach passed in one flow from two cylinder banks. The respective pressuresurges which result in the two paths can thus be used to increase theexhaust-gas feedback rate and the fuel efficiency, provided that areturn flow into the other path is avoided. The return flow is thereforeprevented by non-return valves which, in particular, are integrated inthe exhaust-gas cooler in the outlet area of the second fluid or arearranged in conjunction with a separating plate in the outlet areaadjacent to the outlet opening of the cooler housing, for example byflange connection.

In one development of the invention, multiple-path heat exchangers areformed with a minimum of one direction change for the second fluid. Inthis case, the second fluid is not split into flow elements but ispassed through some of the fluid channels from the inlet end of thesecond fluid to the other end, where this direction is changed, inparticular being changed essentially through 180°, then being passedagain through others of the fluid channels. In this case, the directionmay be changed in a plurality of step elements. However, it is alsopossible to provide a plurality of direction changes, with the secondfluid being output at the inlet end of the heat exchanger if there arean odd number of direction changes, or with the outlet being at theother end of the heat exchanger if there are an even number of directionchanges.

In one development of the invention, the direction change is in the formof a U-flow, with the inlet and the outlet for the second fluid beinglocated closely adjacent to one another at one cooler end, thus allowingthe heat exchanger to be integrated to optimize the physical space.

In one development of the invention, the heat exchanger is in the formof a boost-air intercooler between the compressor stages of a turbineengine, in particular with no separating elements or otherdirection-changing elements being formed in the direction-changing area,since the direction change is produced by a housing that is closed atthis end.

In one development of the invention, no separate bypass tube is requiredfor the U-flow embodiment since, in the bypass mode, the connectionbetween the inlet and outlet connecting stubs is short-circuited in thecombined inlet/output area of the cooler. In the case of cooledexhaust-gas feedback, the path between the inlet and outlet connectingstubs is blocked, and the second fluid, in particular the exhaust gas,is passed through the heat-exchanger channels.

In one development of the invention of the heat exchanger with a U-flow,the design has an internal bypass flap and/or a combination valve and/oran external bypass flap and/or a combination valve. When using anexternal bypass flap in conjunction with a U-flow cooler, theinlet/output area must be split by means of a separating element, andthe bypass flap is then integrated in particular in a module which candirectly short-circuit the path through the exhaust-gas cooler.

As mentioned, the heat exchanger according to the invention can be usedparticularly advantageously as an exhaust-gas cooler; in this case, inparticular, it is advantageous to cool the housing casing, because thecoolant makes direct contact with the housing wall in places and isindirectly connected to the housing wall via material bridges. Dependingon whether it is being used for high-pressure or low-pressureexhaust-gas feedback (exhaust-gas extraction before or after theexhaust-gas turbine), the exhaust-gas cooler can be cooled by thecoolant in the cooling circuit of the internal combustion engine or byair, in which case the flow cross sections and the heat transfer arematched, for example by means of turbulence inserts. When used as anexhaust-gas cooler, it is also advantageous to arrange an oxidationcatalytic converter in the flow direction of the exhaust gas upstream ofthe plate pairs, that is to say in the inlet area of the exhaust-gascooler. It is particularly worthwhile integrating an oxidation catalyticconverter upstream of the heat-exchanger tubes and any bypass flap whichmay be required in the outlet area of the cooler, since theflap/combination valve is then protected against dirt.

The heat exchanger according to the invention can also advantageously beused as a boost-air cooler, either with direct cooling (air) or withindirect cooling (liquid coolant). Furthermore, the heat exchangeraccording to the invention can advantageously be used as acoolant-cooled oil cooler or as an air-cooled condenser for a motorvehicle climate-control system. All that is necessary for the variousapplications is matching to the various media and heat-transferrelationships.

Furthermore, in addition to the two simple types of connectioncomprising flow in the same direction between the first and the secondfluid or flow in the opposite direction between the first and the secondfluid (with the U-flow cooler representing a combination of the two), itis also possible to provide more than one circuit for the first fluid,that is to say for the first medium. For example, in an exhaust-gascooler application, the coolant flow may be carried parallel to theexhaust gas in the inlet area of the exhaust gas, thus achievingeffective boiling prevention, and the coolant flow can be carried in theopposite direction to the exhaust gas in the outlet area of the exhaustgas, thus achieving particularly efficient heat transfer in the rearpart of the heat exchanger, see DE10328746, whose content is herebyexpressly disclosed. The first fluid can be tapped off in the center ofthe heat exchanger through a common outlet for the two circuits, orthrough separate outlets. However, in order to improve the heattransfer, it is also possible, for example, to arrange two circuits onebehind the other for the first medium, with the flow passing throughboth of them in the opposite direction to the second fluid. In thiscase, both circuits for the first medium have their own inlet andoutlet.

Concepts with two circuits for the first fluid flowing in the oppositedirection to the second fluid are particularly worthwhile when the firstand second media have similar thermal capacities, or the second mediumhas a higher thermal capacity than the first, and in particular alsowhen both media are gaseous.

Exemplary embodiments of the invention will be explained in more detailin the following text, and are illustrated in the drawing, in which:

FIG. 1 shows a section through an exhaust-gas cooler according to theinvention with coolant channels in the form of plates,

FIGS. 2 a, 2 b, 2 c show further exemplary embodiments of the design ofthe coolant channels with direct cooling of the housing wall,

FIGS. 3 a, 3 b, 3 c show further exemplary embodiments of the design ofthe coolant channels with indirect cooling of the housing walls,

FIG. 4 shows an exploded illustration of the exhaust-gas cooler withhousing shell, plate pairs and a cover,

FIG. 5 a shows an exploded illustration of the plate pairs and of thecover,

FIG. 5 b shows an exploded illustration of an unjoined plate pair whichcomprises at least one upper plate and at least one lower plate, and afurther lower plate of an adjacent plate pair,

FIG. 5 c shows a section C-C through an exploded illustration of anunjoined plate pair, which comprises at least one upper plate and atleast one lower plate,

FIG. 5 d shows a perspective illustration of a joined plate pair,

FIG. 5 e shows a view of a joined plate pair in the flow direction ofthe second fluid,

FIGS. 6 a, 6 b, 6 c show embodiments of a two-part housing for theexhaust-gas cooler,

FIGS. 7 a, 7 b show longitudinal sections through the exhaust-gas coolerwith different exhaust-gas and coolant routing,

FIGS. 8 a, 8 b show longitudinal sections through the exhaust-gas coolerwith an integrated bypass tube and separating wall in the inlet oroutlet area,

FIG. 9 shows a longitudinal section through an exhaust-gas cooler with abypass tube and an integrated bypass flap,

FIG. 10 shows a longitudinal section through an exhaust-gas cooler witha bypass tube and two separate inlet connecting stubs,

FIG. 11 shows a longitudinal section through an exhaust-gas cooler withan exhaust-gas flow direction change (two-path through-flow),

FIG. 12 shows a longitudinal section through an exhaust-gas cooler witha two-path flow through it and with an integrated bypass with a bypassflap,

FIG. 13 shows a longitudinal section through an exhaust-gas cooler withan oxidation catalytic converter in the exhaust-gas inlet area,

FIG. 14 shows a longitudinal section through an exhaust-gas cooler withtwo paths and in each case one non-return valve for each path in theoutlet area of the second fluid,

FIG. 15 shows a longitudinal section D-D through two crimped and joinedplate pairs, and

FIG. 16 shows a longitudinal section through an exhaust-gas cooler witha change in the direction of the exhaust-gas flow (two-path flow throughit), with the fluid in one path entering the exhaust-gas cooler, andemerging from the exhaust-gas cooler through the other path.

FIG. 1 shows a heat exchanger 1 according to the invention which is inthe form of an exhaust-gas cooler and can be used in an exhaust-gasfeedback system for an internal combustion engine for motor vehicles.Exhaust-gas feedback systems are known from the prior art: in this case,the exhaust gas from the internal combustion engine is tapped offupstream or downstream of an exhaust-gas turbine (high-pressure orlow-pressure feedback), and is supplied again to the induction manifoldof the internal combustion engine having been cooled in one or twostages. The amount of exhaust gas tapped off is controlled by anexhaust-gas feedback valve. Exhaust gas flows through the illustratedexhaust-gas cooler 1 and is cooled by a liquid coolant which ispreferably taken from the cooling circuit of the internal combustionengine. The exhaust-gas cooler 1 has a two-part housing 2 whichcomprises a housing shell 2 a in the form of a trough and a cover 2 b—inwhich case both parts are preferably in the form of sheet-metal partsand can be produced by thermoforming or deep-drawing. A pack of platepairs 3 is arranged in the housing shell 2 a, and the coolant flowsthrough it. The plate pairs 3 extend over the entire width of thehousing shell 2 a, which has two housing walls 2 c and 2 d, which areillustrated at right angles in the drawing, and run parallel to oneanother. The plate pairs 3 have longitudinal faces 3 a which rest on thehousing walls 2 c, 2 d, and form flow channels which are fitted withturbulence inserts 4 in order to increase the heat transfer. The platepairs 3 are arranged parallel and at a distance from one another, andform channels 5 for the exhaust gas to pass through. Turbulence inserts6 are arranged in the channels 5 for the exhaust gas to pass through, inorder to increase the heat transfer. All of the parts of the exhaust-gascooler 1 are integrally connected to one another, that is to say bymeans by soldering. The soldering is preferably carried out in oneprocess in a solder oven that is not illustrated. The plate pairs eachhave an upper plate 80 b and a lower plate 80 c.

FIG. 2 a shows a further exemplary embodiment of the invention in theform of a detail comprising an exhaust-gas cooler, with the samereference numbers as in FIG. 1 being used for the same parts. Two platepairs 7 are arranged between the two housing walls 2 c, 2 d, facing awayfrom one another and connected by their longitudinal faces 7 a to thehousing walls 2 c, 2 d, by soldering. The plate pairs 7 each comprise anupper plate 7 b and a lower plate 7 c, which are connected to oneanother by a fold at the rim. The flow cross section through which thecoolant flows extends to the housing walls 2 c, 2 d and thus providescooling for the housing walls which are heated by the exhaust-gas flow.

FIG. 2 b shows a further exemplary embodiment of the invention relatingto the design of a plate pair 8 which is composed of an upper plate 8 a,80 b and a lower plate 8 b, 80 c and is closed at the side by arespective fold 8 c. The flow cross section of the plate pair 8 isextended at the side to form side channels 8 d, 8 e which areapproximately the same height as the exhaust-gas channels 5 and theturbulence inserts 6 which are arranged in the exhaust-gas channels 5.The side channels 8 d, 8 e through which the coolant flows thereforeextend from one plate pair 8 to the adjacent plate pair, and rest overtheir entire area on the housing walls 2 c, 2 d. This results in verygood cooling of the housing walls 2 c, 2 d, which are thereforeinsulated from the exhaust-gas flow. The same features are provided withthe same reference symbols as in the previous figures.

FIG. 2 c shows a further embodiment of the plate pairs 9, comprising anupper plate 80 b and a lower plate 80 c, between housing walls 2 c, 2 d,with an extension of the flow cross section forming side channels 9 a, 9b, although these are not as high as the exhaust-gas channels, but areonly a portion of its height, for example 50%, with the rest of thechannel height in each case being bridged by a longitudinal fold 9 c, 9d. This embodiment also results in very good cooling of the housingwalls 2 c, 2 d, since coolant flows around them. The same features areprovided with the same reference symbols as in the previous figures.

FIGS. 3 a, 3 b, 3 c show further exemplary embodiments of the inventionof embodiments of plate pairs 10, 11, 12 which are each formed from anupper plate 80 b and a lower plate 80 c, whose flow channels have awidth b which is less than the unobstructed width w of thehousing—material bridges 10 a, 10 b, 11 a, 11 b, 12 a, 12 b which eachrun in the longitudinal direction are arranged between the flow channelsof the plate pairs 10, 11, 12 and, in each case in differentembodiments, rest on the housing walls 2 c, 2 d and are soldered tothem. This likewise results in a good cooling effect, that is to say thehousing walls 2 c, 2 d are cooled indirectly, that is to say by thermalconduction via the material bridges 10 a, 10 b, 11 a, 11 b, 12 a, 12 b.The same features are provided with the same reference symbols as in theprevious figures.

FIG. 4 shows a 3D illustration of the individual parts of an exhaust-gascooler which corresponds to the exemplary embodiment shown in FIG. 1.The same features are provided with the same reference symbols as in theprevious figures. A housing shell 13 in the form of a trough is shown atthe bottom of the drawing, and has an exhaust-gas inlet opening 13 a atthe end, that is to say on its narrow face, and an exhaust-gas outletopening 13 b on the opposite narrow face (the majority of which isconcealed). Three plate pairs 14, a cover plate 15 and the housing cover16 are shown above the housing shell 13. The approximately rectangularplate pairs 14 have angled rim strips 14 a, which are in the form offolds and can be soldered to the inside of the housing shell 13, on eachof their longitudinal faces. Coolant flows through the plate pairs 14and they therefore have depression-like protrusions 14 b, 14 c, which,in the soldered state, respectively form an inlet channel and an outletchannel for the plate pairs, through which flow can then pass parallelto one another. The coolant connections (not shown here) are located inthe cover 16 of the housing. As can also be seen from this illustration,the individual parts of the exhaust-gas cooler can be joined andprepared for the soldering process in a simple manner.

FIG. 5 a shows a further illustration of the plate pairs 14 shown inFIG. 4, viewed from the front, that is to say seen in the flow directionof the exhaust gas. The same reference numbers are used as those in FIG.4. The plate pairs 14 are arranged parallel and at a distance from oneanother and form approximately rectangular flow channels (channels forthe flow to pass through) 17 for the exhaust gas, with turbulenceinserts, as illustrated in FIGS. 1 to 3, in this case having beenomitted. The plate pairs 14 each comprise two plates, specifically anupper plate 14 d and a lower plate 14 e, which are connected to oneanother on each of their longitudinal faces by the angled fold 14 a. Theend faces 14 f, which form the inlet flow edges for the exhaust gas, arein contrast connected to one another by a flat fold. The plate pairs 14are therefore circumferentially sealed at the rim. The depression-likeprotrusions 14 b are formed from the upper plate 14 d and rest on theadjacent lower plate 14 e-thus creating an inlet-flow and an outlet-flowchannel, which run transversely with respect to the exhaust-gas flowdirection, for the coolant. The protrusions are streamlined in order toachieve a small pressure drop on the exhaust-gas side, for example as isshown in FIG. 4 with an oval or elliptical cross section. Apart fromthis, depending on the application, structure elements in the form ofbeads or so-called winglets can also be formed in the plates, instead ofthe turbulence inserts.

FIG. 5 b shows an exploded illustration of an unjoined plate pair 3, 14which comprises at least one upper plate 80 b and at least one lowerplate 80 c, as well as a further lower plate 80 c of an adjacent platepair. The same features are provided with the same reference symbols asin the previous figures. The upper plate 80 b and the lower plate 80 ceach have a plate opening 81, which is in the form of a hole. The upperplate 80 b has at least one protrusion 14 b, in particular twoprotrusions 14 b, which are in the form of truncated cones in thestacking direction. The truncated cone has an upper plate annularsurface 82, 82 c on the side with the smallest external diameter, whichupper plate annular surface 82, 82 c is arranged parallel to the platesurface 92 of the upper plate 80 b and of the lower plate 80 c, and atright angles to the stacking direction of the plate pairs 3, 14. Thelower plate 80 c has a lower plate annular surface 83, 83 c, which isformed integrally with the plate surface 92 and is identical to it inthe area of the plate opening. In the joined state, in particular in thesoldered, welded, adhesively bonded, etc. state, the upper plate annularsurface 82, 82 c of a plate pair 3, 14 and the lower plate annularsurface 83, 83 c of an adjacent plate pair 3, 14 touch, and areintegrally connected to one another. The upper plate 80 b has an upperplate rim surface 85 at the plate rims. The lower plate 80 c has a lowerplate rim surface 86 at the plate rims. The upper plate rim surface 85and the lower plate rim surface 86 correspond to one another and areintegrally connected to one another, in particular by soldering,welding, adhesive bonding etc. The upper plate rim surface 85 runs inthe longitudinal direction of the plate essentially parallel to thelower plate rim surface 86, in the same way as the upper plate rimsurface 85 in the direction of the plate width, which runs essentiallyparallel to the lower plate rim surface, in particular alignedessentially at right angles to the longitudinal direction of the plateand essentially at right angles to the stacking direction of the plates.An abutment 93 between the lower plate rim surface and the upper platerim surface is formed in those sections of the upper plate rim surfaceand of the lower plate rim surface in which the longitudinal face of theplate merges into the plate width in the stacking direction, such thatthe abutment 93 of one plate rim surface is essentially in the form of aquarter cylinder in the longitudinal direction, and such that thequarter cylinders of the lower plate and upper plate touch essentiallylike two concentric quarter cylinders which have been pushed one insidethe other, and are integrally connected to one another, in particular bysoldering, welding, adhesive bonding etc.

FIG. 5 c shows a section C-C through the exploded illustration in FIG. 5b of an unjoined plate pair, which has at least one upper plate 80 b andat least one lower plate 80 c. The same features are provided with thesame reference symbols as in the previous figures.

FIG. 5 d shows a perspective illustration of a joined plate pair 3, 14.The same features are provided with the same reference symbols as in theprevious figures. In the joined state, in particular in the soldered,welded, adhesively bonded etc. state, the upper plate annular surface82, 82 c of a plate pair 3, 14 and the lower plate annular surface 83,83 c of an adjacent plate pair 3, 14 touch and are integrally connectedto one another. At the plate rims, the upper plate 80 b has an upperplate rim surface 85. The lower plate 80 c has a lower plate rim surface86 at the plate rims. The upper plate rim surface 85 and the lower platerim surface 86 correspond to one another and are integrally connected toone another, in particular by soldering, welding, adhesive bonding etc.The upper plate rim surface 85 runs essentially parallel to the lowerplate rim surface 86 in the longitudinal direction of the plate, in thesame way as the upper plate rim surface 85 runs in the direction of theplate width, essentially parallel to the lower plate rim surface, and inparticular is aligned essentially at right angles to the longitudinaldirection of the plate and essentially at right angles to the stackingdirection of the plates. An abutment 93 between the lower plate rimsurface and the upper plate rim surface is formed in those sections ofthe upper plate rim surface and of the lower plate rim surface in whichthe longitudinal face of the plate merges into the plate width in thestacking direction, such that the abutment 93 of the plate rim surfaceis essentially in the form of a quarter cylinder in the longitudinaldirection, and in such a way that the quarter cylinders of the lowerplate and upper plate essentially touch one another like two concentricquarter cylinders which have been pushed one inside the other, and areintegrally connected to one another, in particular by soldering,welding, adhesive bonding etc.

FIG. 5 e shows a view of a joined plate pair in the flow direction ofthe second fluid. The same features are provided with the same referencesymbols as in the previous figures.

FIGS. 6 a, 6 b, 6 c show different forms of the embodiment of housings17, 18, 19, which each have housing shells 17 a, 18 a, 19 a in the formof boxes or troughs. The same features are provided with the samereference symbols as in the previous figures. The cover shapes 17 b, 18b, 19 b are different. The cover 17 b has a circumferential bead(groove) 17 c, which can be placed on the circumferential upper edge ofthe housing shell 17 a, and can thus be soldered. The cover 18 b has acircumferential rim 18 c which projects upwards and rests on the innerwall of the housing shell 18 a. The cover 18 b can thus “sag” duringsoldering (during melting of the solder layers in the plate pack). Thecover 19 b has an angled rim 19 c, which clasps the outside of the upperedge of the housing shell 19 a and can therefore also be solderedcircumferentially. All the illustrated parts can be produced at low costas deep-drawn or thermoformed parts.

FIG. 7 a shows an exhaust-gas cooler 20 in the form of a longitudinalsection with a housing 21, comprising a housing shell 21 a, a cover 21b, an inlet for the first fluid 90 and an outlet for the first fluid 91.A pack 22 (illustrated by dashed lines) comprising the already mentionedplate pairs, which are not illustrated here but through which coolantcan flow, is arranged in the housing 21. The same features are providedwith the same reference symbols as in the previous figures. The relevantcoolant connections are arranged as connecting stubs 23, 24 in the cover21 b of the housing 21. The exhaust gas, represented by arrows A, entersthe exhaust-gas cooler 20 through an inlet connecting stub 25, andleaves it via an outlet connecting stub 26. An inlet area 27 isincorporated in the exhaust-gas flow direction upstream of the platepack 22 and acts as a diffuser, and an outlet area 28 is incorporated inthe housing 21 downstream from the plate pack 22, and merges into theoutlet connecting stub 26. The exhaust gas, represented by the arrows A,therefore flows essentially in the longitudinal direction (“axially”)through the exhaust-gas cooler 20 and through the plate pack 22.

FIG. 7 b shows a similar exhaust-gas cooler 29 with the difference thatthe coolant connections 30, 31 are arranged in the base part of thecooler, and the exhaust-gas connecting stop 32 on the outlet side isarranged in the cover part of the housing, thus making it possible tochange the direction of the emerging exhaust gas through 90°,represented by an arrow A. The same features are provided with the samereference symbols as in the previous figures. Changes such as these inthe exhaust-gas and coolant inlet and outlet are therefore possible bysimple measures on the housing. FIGS. 7 a, 7 b show exhaust-gas andcoolant flows in the same direction. However, it is also possible forthe two media to flow in opposite directions to one another.

FIGS. 8 a and 8 b show further exemplary embodiments of the invention,to be precise an exhaust-gas cooler 33 with a bypass channel 34 arrangedat the bottom, and an exhaust-gas cooler 35 with a bypass channel 36arranged at the top. The same features are provided with the samereference symbols as in the previous figures. The two bypass channels35, 36 may be in the form of a tube and may be introduced into thehousing, in each case parallel to the plate packs 37 a, 37 b, which areillustrated in shaded form. In the exhaust-gas inlet area, theexhaust-gas cooler 33 shown in FIG. 8 a has a separating or sealingelement 38, which is used to separate the exhaust-gas flow into two flowelements for the plate pack 37 a on the one hand and the bypass tube 34on the other hand. The exhaust-gas cooler 35 shown in FIG. 8 b has anexhaust-gas supply with a direction change through 90° from the coverside, corresponding to which an angled separating element 39 is arrangedin the exhaust-gas inlet area, and seals the exhaust-gas flow elementsfrom one another. A bypass valve, which is not illustrated, is thereforearranged outside the exhaust-gas cooler in both cases.

FIG. 9 shows a further exemplary embodiment of the invention in the formof an exhaust-gas cooler 40 with a plate pack 41 and a bypass channel 42arranged under it, with a bypass flap 43, which can pivot, beingarranged in the exhaust-gas inlet area, represented by the exhaust-gasarrow A. The same features are provided with the same reference symbolsas in the previous figures. The exhaust-gas flow can therefore be passedeither through the plate pack 41 or through the bypass channel 42, withintermediate positions also being possible. The design of a bypass flapis known from the prior art, and is also referred to as an exhaust-gasswitch.

FIG. 10 shows a further exemplary embodiment of the invention in theform of an exhaust-gas cooler 44 with a plate pack 45 (heat-exchangerpart) and a bypass channel 46 arranged at the top, each of which haveseparate associated exhaust-gas inlets 47, 48 in the housing of theexhaust-gas cooler 44. The same features are provided with the samereference symbols as in the previous figures. A separating element orseparating wall 49 is arranged between the two exhaust-gas inlets 47,48, and can be soldered to the housing.

FIG. 11 shows a further exemplary embodiment of the invention in theform of an exhaust-gas cooler 50 through which flow passes on two pathsand which has a plate pack 51 (heat-exchanger part), an exhaust-gasinlet chamber 52, an exhaust-gas outlet chamber 53, which is separatedby a separating wall, and a deflection chamber 54 for the exhaust-gasflow, represented by an elongated U-shaped arrow A. The same featuresare provided with the same reference symbols as in the previous figures.

FIG. 12 shows a further exemplary embodiment of the invention,specifically an exhaust-gas cooler 55 through which the flow passes ontwo paths and which has an exhaust-gas chamber 56 with an exhaust-gasinlet connecting stub 57 and an exhaust-gas outlet connecting stub 58.The same features are provided with the same reference symbols as in theprevious figures. An exhaust-gas flap 59 (solid line) which can pivot isarranged in the exhaust-gas chamber 56 and can be pivoted to a position59′ represented by dashed lines. In the position 59, the inletconnecting stub 57 and the outlet connecting stub 58 are separated fromone another, that is to say the exhaust-gas flow flows through theheat-exchanger part 60 corresponding to the U-shaped arrow A, andemerges through the exhaust-gas connecting stub 58; the entireexhaust-gas flow is therefore cooled. In the situation in which noexhaust-gas cooling is required, the exhaust-gas flap 59 is moved to theposition 59′ represented by dashed lines, so that the exhaust-gas flowentering the inlet connecting stub 57 is passeddirectly—short-circuited—into the outlet connecting stub 58, and emergesfrom the exhaust-gas cooler 55. The exhaust-gas chamber 56 thereforeforms a bypass channel, represented by a dashed arrow B. The plate pack60 can therefore be bypassed in the bypass. The exhaust-gas cooler 55therefore has an integrated bypass, with an integrated bypass flap.

As a further exemplary embodiment of the invention, FIG. 13 shows anexhaust-gas cooler 61 with a heat-exchanger part 62 (plate pack) throughwhich exhaust gas can flow on one path (“axially”), corresponding to theexhaust-gas arrows A. The same features are provided with the samereference symbols as in the previous figures. The exhaust-gas cooler 61has an exhaust-gas inlet area 63, which is in the form of a diffuser andin which an oxidation catalytic converter 64 is arranged which, as isknown from the prior art, is used for exhaust-gas purification. Inaddition to the space-saving design, this arrangement has the advantagethat the exhaust-gas channels in the oxidation catalytic converter,which are not illustrated, allow the exhaust-gas flow to be carried inone direction and therefore allow this flow to be passed in a bettermanner to the downstream plate pack 62.

FIG. 14 shows a longitudinal section through an exhaust-gas cooler withtwo paths, and in each case a non-return valve for each path, in theoutlet area of the second fluid. The same features are provided with thesame reference symbols as in the previous figures. A first path 87 ofthe second fluid enters the inlet area of the second fluid into the heatexchanger and, in particular, this first path 87 is in the form of abypass, as well as a second path 88 for the second fluid. The first path87 and the second path 88 are separated from one another, such that theyare sealed, by a sealing element 89 in the form of a separating wall.The sealing element 89 is designed to be streamlined for the secondfluid, such that the paths which enter the heat exchanger at an angle tothe plate longitudinal direction are passed through the radiused sealingelement to the inlet to the plate pack in the plate longitudinaldirection. A first non-return valve 94 for the first path and a secondnon-return valve 95 for the second path are integrated in particular inthe outlet area of the heat exchanger and are designed such that thefirst non-return valve 94 has a first rotating joint 98 adjacent to thehousing base which allows a pivoting movement of a first valve flap 96about a rotation axis which is arranged parallel to the plate width andat right angles to the plate longitudinal direction. The secondnon-return valve 95 has a second rotating joint 99, which is arrangedadjacent to the housing cover and allows a pivoting movement of a secondvalve flap 97 about a rotation axis which is arranged parallel to theplate width and at right angles to the plate longitudinal direction.This prevents the second fluid from flowing back from the outlet areainto the plate pack.

FIG. 15 shows a longitudinal section D-D through two crimped and joinedplate pairs. The same features are provided with the same referencesymbols as in the previous figures. The upper plates 80 b and the lowerplates 80 c are arranged essentially parallel and at a distance from oneanother, with the distance between an upper plate 80 b and a lower plate80 c of a plate pair 3, 14 forming the height of the flow channel forthe first fluid, and the distance between a lower plate 83 and the upperplate 82 of an adjacent plate pair forming the height of the channel forthe second fluid to pass through. The lower plates 81 c have an opening81, around which a lower plate annular surface 83 is formed,concentrically. The upper plates 81 b likewise have an opening 81.Conical protrusions 14 b are formed conically in the area of theseopenings, at right angles to the plate surface and out of the upperplates in the stacked-plate direction. The protrusion bends in thesection of the protrusion 14 b with the smaller of the two conediameters which are located at the two cone ends, and runs parallel tothe plate surface, thus forming an upper plate annular surface 82 whichtouches the lower plate annular surface 83 of an adjacent plate pair,and is integrally connected to it, in particular by soldering, welding,adhesive bonding, etc. The upper plates bend beyond the protrusions 14 bin the direction of the inlet area for the second fluid in the directionof the housing base. The height of the flow channel decreases until theupper plate 80 b and the lower plate 80 c of a plate pair touch and runparallel to one another, and are integrally connected to one another, inparticular by soldering, welding, adhesive bonding etc. The lower plate80 c projects somewhat beyond the length of the upper plate 80 b in thelongitudinal direction, thus creating an end-width area 101 of the lowerplate 80 c which is bent around the associated upper plate 80 b of theplate pair 3, 14, at least in places, over the entire plate width, andtherefore clasps the upper plate, which is referred to as crimping. Thecrimping also reduces the flow losses at the inlet of the second fluidto the plate pairs in comparison to the inlet arriving at an edge. Inthe same way, the lower plates are crimped to the upper plates at leastin places over the entire plate width on the outlet side of the platepack, although this is not illustrated in FIG. 15. The crimping is alsocarried out at least in places over the two longitudinal faces of theplates, although this is likewise not illustrated in FIG. 15. In afurther embodiment which is not illustrated, the upper plate can alsoclasp the lower plate.

FIG. 16 shows a longitudinal section through an exhaust-gas cooler withthe direction of the exhaust-gas flow being changed (flow through it ontwo paths), with the fluid entering the exhaust-gas cooler on one path,and leaving the exhaust-gas cooler through the other path. The samefeatures are provided with the same reference symbols as in the previousfigures. The inlet and the outlet of the second fluid are located on oneof the same sides of the heat exchanger. They are separated from oneanother, with a seal, by a sealing element 89, which is in the form of awall. The second fluid enters the heat exchanger through theinlet/outlet area and its direction is changed as a U-flow, with thesecond fluid flowing in the opposite direction to the outlet area, andleaving the heat exchanger. The inlet and the outlet for the secondfluid are arranged close to one another at one cooler end, thus allowingthe heat exchanger to be integrated, in an optimum physical space.

The turbulence-generating elements and the turbulence inserts are in theform of web ribs in a further embodiment, which is not illustrated.

Turbulence inserts with web ribs have comparatively less tendency toaccumulate deposits despite their flow cross sections beingfundamentally smaller than those of other inserts. In principle, therewas a concern that turbulence inserts with web ribs would lead toincreased blocking of individual channels for the flow to pass through,owing to the fine-element structure of the web ribs. However, this istrue to a surprisingly small extent, particularly if the webs of the webribs are relatively short. One possible explanation for this could bethat the turbulent flow which is created over large parts of the web-ribinsert in the exhaust gas reduces the deposition of particles while incontrast organized flows are formed in longer, single-form channels,which promote the deposition of particles close to walls, because theflow speed is very low there.

Re FIGS. 1 to 16

In one preferred embodiment, the webs of the web ribs have a lengthwhich is no more than about 10 mm, preferably no more than about 5 mm,and particularly preferably no more than about 3 mm. Depending on theavailable physical space and the internal combustion engine, there maybe specific requirements for the pressure drop across the exhaust-gasheat exchanger. One of the abovementioned length ranges may bepreferred, depending on these requirements.

Furthermore, the density of the web ribs transversely with respect tothe exhaust-gas flow direction is preferably between about 20 web ribsper dm and about 50 web ribs per dm, preferably between about 25 webribs per dm and 45 web ribs per dm. These web rib densities have beenfound to be particularly suitable in trials. In particular, the web ribsparticularly advantageously represent a good compromise between the riskof blocking and cooling performance.

With respect to the height of the web ribs, it should be rememberedthat, if they are high, only relatively small primary areas, that is tosay surfaces cooled by coolant, are available, via which all of the heatmust be dissipated into the coolant. If the primary areas are relativelysmall, the risk of a liquid coolant burning is then increased.Furthermore, the efficiency of the inserts decreases as the height ofthe web ribs increases. A preferred height for the insert or web rib istherefore between about 3.5 mm and about 10 mm, particularly preferablybetween about 4 mm and about 8 mm, and in particular preferably betweenabout 4.5 mm and about 6 mm.

In one preferred development of the apparatus according to theinvention, it is possible for an oxidation catalytic converter to bearranged upstream of the plurality of flow channels. In general, acatalytic converter such as this makes it possible to reduce theparticle sizes, particle densities and the proportions of hydrocarbonsin the exhaust gas, by oxidation. In this case, additionally oralternatively, it is possible to provide for the inserts themselves tobe provided with a coating for catalytic oxidation of the exhaust gas.Particularly in conjunction with oxide-catalytic means, the web ribdensities that can sensibly be used transversely with respect to theexhaust-gas flow direction may be more than about 50 web ribs per dm, inparticular about 75 web ribs per dm. This will result in particularlygood heat-exchanger performance for a given physical space without thelong-term risk of blocking as a result of deposits.

In one particularly preferred embodiment, the web ribs have inclinedteeth. Ribs with inclined teeth have been found experimentally to beparticularly suitable for ensuring good long-term stability of theexhaust-gas heat exchanger against deposits. In this case, in onepreferred embodiment, the angle between the web walls and a maindirection of the web ribs is between about 1° and about 45°. In oneparticularly preferred embodiment the angle is between about 5° andabout 25°, although, in an alternative preferred embodiment, it may alsobe between about 25° and about 45°. The first-mentioned value range from5° to 25° is particularly highly suitable for normal applications, whichare particularly sensitive to pressure losses, with the second-mentionedvalue range being suitable to achieve an optimized power density, inparticular for applications which are less sensitive to pressure losses.

In general, a correlation can be found between the angle of the wallsand a longitudinal pitch of the web ribs for optimization of an insertwith obliquely toothed web ribs. In this case, in particular, optimumembodiments with small angles may have greater pitches 1 than optimizedembodiments with large angles. Embodiments with a moderate pressure lossresult in particular with small inclination angles. Embodiments withoptimized power density can be obtained in particular with largeinclination angles. Particularly in the case of small inclinationangles, the longitudinal pitch may be greater while, for largeinclination angles, the longitudinal pitch may in particular be less, inorder to obtain optimized embodiments.

In one preferred embodiment, the apparatus is in the form of astacked-plate heat exchanger. This embodiment is particularlyappropriate both in terms of the width of a flow channel and in terms ofcost-effective manufacture and the capability to combine aheat-exchanger housing with web-rib inserts. Alternatively, theapparatus may, however, also be in the form of a tube-bundle heatexchanger, or may be some other heat-exchanger form that is known perse.

It is generally preferable for the insert to be manufactured from astainless steel, in particular from an austenitic steel, in order toprevent corrosion being caused by the corrosive exhaust gas.

In a further advantageous refinement, aluminum materials may be used, inwhich case it may then be particularly advantageous to provide suitablecorrosion protection, in particular such as an alloy and/or a coating.

In one advantageous embodiment, the insert is formed from aluminum.Inserts formed from aluminum have a particularly light weight. It isparticularly advantageous to form the inserts from aluminum by means ofan alloy or coating, for corrosion protection.

Depending on the flow parameters, in particular the Reynolds number, thelength of inlet area of the flow channels, in particular tubes and/orstacked-plate pairs, 1/s is approximately 2.5 to 5, and the length ofthe web ribs must be chosen to be below this limit value. S denotes themean cross-sectional width between two webs, and is therefore b/2-t,where t is the metal-sheet thickness. This results in a required ratio1/s of less than 4, in particular 1/s of less than 2. If there is a highrisk of blocking as a result of a critical exhaust-gas composition, 1/sshould be chosen to be less than 1.5, in particular 1/s<1.

The inclined position of the webs results in a higher flow speed on thewall on the swirl side, counteracting particulate deposits. A furthermajor advantage of web ribs with inclined teeth is that, in situationsin which a low web-rib density in the direction at right angles to theflow is necessary in order to avoid blocking, particularly with a poorexhaust-gas composition, adequate cooler performance can be ensureddespite a small rib surface area.

The stacked-plate heat exchanger according to the invention has an outerhousing with a cover, with an inlet and an outlet being provided for theexhaust gas, as well as an inlet and an outlet for a liquid coolant. Aplurality of plate elements are provided within the housing, with eachof the plate elements comprising an upper half and a lower half. Theplate elements are welded to one another and to the housing by means ofcollars that are placed on them, such that the coolant in each caseflows from the inlet to the outlet between the two halves of one plateelement. An insert, which is not shown but has web ribs, is arrangedbetween two plate elements in each case, with the intermediate spacebetween two plate elements in each case forming a flow channel for theexhaust gas. The inserts are not illustrated, for clarity reasons. Theinserts are composed of a stainless steel. In order to improve thethermal contact between the inserts and the plate elements and/or thehousing, the inserts may be welded or soldered flat to the saidelements.

In a further embodiment, the turbulence insert is formed from a thinsheet-metal material, in which parallel web ribs are incorporated byforming measures. Each of the web ribs has a row of webs arranged oneafter the other in the exhaust-gas flow direction. Two webs which followone another in the exhaust-gas flow direction are in each case arrangedoffset with respect to one another through half the web widthtransversely with respect to the exhaust-gas flow direction, so thateach web is followed by a sharp edge followed by a web. In the presentexample, the walls are aligned parallel to the flow direction of theexhaust gas and form an angle of 0° with an axis B of the web ribs andthe main flow direction of the exhaust gas A. A web rib insert such asthis is referred to as a straight-toothed web rib.

In the first exemplary embodiment, the length 1 of a web is about 4 mm.The width b of a single web rib is defined as the width of the cyclicunit of the periodic structure transversely with respect to the mainflow direction of the exhaust gas. The web rib density 2/b in thepresent example is about 40 web ribs per dm. The width b of a web rib isthus about 5 mm.

The height h of the web ribs corresponds to the distance between twoadjacent plate elements of the heat exchanger, and in the present caseis about 5 mm.

In a further refinement of the web-rib insert, the side walls of theindividual webs are in this case not aligned parallel to the maindirection B of the web ribs. In fact, each of the walls of the websincludes an angle W of about 30° with the main direction B of the webribs. The further dimensions of the obliquely toothed web-rib insertscorrespond to the dimensions of the straight-toothed web rib.

Suitable longitudinal pitches 1 for corresponding angles of the walls Win suitable embodiments are 10° with longitudinal pitches 1 of less thanabout 10 mm, 20° with 1 less than about 6 mm, 30° with 1 less than about4 mm, and 45° with 1 less than about 2 mm.

The minimum longitudinal pitch 1 is about 1 mm for all angles. Thepermissible channel extent 1/s is within approximately the same limit asthat for straight-toothed web ribs, with s being the web separationtransversely with respect to the main flow direction B. It is generallydifficult to produce longitudinal pitches 1 of less than 1 mm, formanufacturing reasons.

The at least one heat exchanger is at least one exhaust-gas heatexchanger and/or a boost-air cooler and/or an oil cooler and/or acoolant cooler and/or a coolant condenser for a climate-control systemand/or a gas cooler for a climate-control system and/or a coolantvaporizer for a climate-control system and/or a cooler for coolingelectronic components.

In a first embodiment, the boost-air cooler and/or exhaust-gas cooler isa direct boost-air cooler and/or direct exhaust-gas cooler. In thiscase, direct should be understood as meaning that at least one medium tobe cooled, such as exhaust gas and/or boost air, is cooled directly by acooling medium such as air.

In a second embodiment, the boost-air cooler and/or exhaust-gas cooleris an indirect boost-air cooler and/or indirect exhaust-gas cooler. Inthis case, indirectly should be understood as meaning that at least onemedium to be cooled, such as exhaust gas and/or boost air, is cooled bya coolant such as a fluid containing water and/or a liquid such ascooling water, with this fluid containing water and/or the liquid suchas cooling water being cooled by some other cooling medium, such asambient air.

The at least one boost-air cooler in another embodiment is cooleddirectly and the at least one exhaust-gas cooler is cooled indirectly,or vice versa the at least one boost-air cooler in another embodiment iscooled indirectly, and the at least one exhaust-gas cooler is cooleddirectly.

In order to improve the heat transfer, in a further embodiment, at leasttwo circuits, in particular two, three, four or more circuits, for thefirst medium are stacked one behind the other, that is to say inparticular they are stacked in the direction A and/or in the stackingdirection in which the plates are stacked, which in particular farms anangle 0° to 90° with the direction A. For example, the two, three, fouror more than four circuits may have flow passing through them inopposite directions or in the same direction, or at an angle of 0° to90° to the second fluid, in particular to the flow direction of thesecond fluid.

If the at least two circuits, in particular two, three, four or morethan four circuits, for the first medium are arranged one behind theother, that is to say in particular in the direction A, at least onehigh-temperature circuit is arranged first flowing in the direction A,and is at a higher temperature than an at least second low-temperaturecircuit. In particular, the temperature difference between thehigh-temperature circuit and the low-temperature circuit is 10K to 100K,in particular 30K to 80K, more particularly 30K to 60K.

The high-temperature circuit is at temperatures between 70° C. and 100°C., in particular between 80° C. and 95° C., in particular in theoperating state. The low temperature is at temperatures between 10° C.and 70° C., in particular between 20° C. and 60° C., in particularbetween 30° C. and 65° C., and more particularly between 40° C. and 50°C., in particular in the operating state.

In this way, the exhaust gas that is fed back and/or the boost air or atleast one medium to be cooled is cooled in two, three, four or morestages.

The at least two circuits, in particular two, three, four or morecircuits for the first medium are in the form of at least one U-flowcircuit and/or at least one I-flow circuit. For example, at least twoI-flow circuits or at least two U-flow circuits are arranged in series,in particular one after the other. In another example, at least oneU-flow circuit follows at least one I-flow circuit, or vice versa. Inparticular, when at least two U-flow circuits are provided, the coolantconnections for the at least two circuits are in one example arranged onone side of the cooler, for example at the top or bottom in the stackingdirection of the plates, or at an angle of between 0° and 90° to thestacking direction.

In another example, the forward flow takes place in at least onehigh-temperature circuit, and the return flow in the at least onelow-temperature circuit, or vice versa.

Furthermore, in another embodiment, a combination valve is integrated inthe at least one heat exchanger, for example in the exhaust-gas heatexchanger and/or in the at least one boost-air cooler and/or in the atleast one oil cooler and/or in the at least one coolant cooler and/or inthe at least one coolant condenser for a climate-control system and/orin the at least one gas cooler for a climate-control system and/or inthe at least one coolant vaporizer for a climate-control system and/orin the at least one cooler for cooling electronic components, inparticular integrated in the housing of the heat exchanger, and/orformed integrally with it. The combination valve combines the functionof at least one exhaust gas feedback valve for open-loop and/orclosed-loop control of the fed-back exhaust gas or exhaust gas/airmixture, and/or the function of at least one bypass valve, in particulara bypass flap, for bypassing exhaust gas that has been fed back aroundthe at least one heat exchanger, in particular the exhaust-gas heatexchanger and/or one of the other heat exchangers mentioned furtherabove, so that a medium which is fed back, in particular exhaust gasand/or air, is not cooled in the at least one heat exchanger, inparticular the exhaust-gas heat exchanger and/or one of the other heatexchangers mentioned further above. A combination valve such as this isdisclosed in the unpublished DE 10 2005 034 136.5, the unpublished DE 102005 041 149.5, the unpublished DE 10 2005 041 150.9, the unpublished DE10 2005 034 135.7 and in the published DE 103 21 636, the published DE10321637 and the published DE 10 2005 041 146, whose entire content ishereby expressly regarded as disclosed.

The features of various exemplary embodiments can be combined with oneanother as required. The invention can also be used for fields otherthan those described.

1. A heat exchanger having flow channels through which a first fluid canflow from a common first inlet to a common first outlet, having ahousing which holds the flow channels in it and through which a secondfluid, which differs from the first fluid (alternatively: and a secondfluid different from the first fluid), can flow from a second inlet areato a second outlet area, with the flow channels having a flat crosssection and longitudinal faces, wherein the longitudinal faces of theflow channels are integrally connected to the housing.
 2. The heatexchanger as claimed in claim 1, wherein the flow channels areintegrally connected to the housing essentially over the entire lengthof the longitudinal faces.
 3. The heat exchanger as claimed in claim 1,wherein flow channels are in the form of plate pairs and, in conjunctionwith the housing, form channels for the second fluid to pass through. 4.The heat exchanger as claimed in claim 1, wherein the flow channels andthe channels for the second fluid to pass through are essentiallyaccommodated in their entirety by the housing.
 5. The heat exchanger asclaimed in claim 1, wherein at least one flow channel for the firstfluid is formed between a cover and a lower plate which is adjacent tothe cover.
 6. The heat exchanger as claimed in claim 1, wherein at leastone flow channel for the first fluid is formed between an upper plate,which is adjacent to a base section of a housing shell, and between thebase section of the housing shell.
 7. The heat exchanger as claimed inclaim 1, wherein the plate pairs have a lower plate and an upper platewhich are connected to one another at the rim by a fold.
 8. The heatexchanger as claimed in claim 1, wherein at least one inlet flow channeland/or at least one outlet flow channel run/runs transversely throughthe plate pairs.
 9. The heat exchanger as claimed in claim 1, whereinthe plate pairs have at least one depression or at least one protrusion.10. The heat exchanger as claimed in claim 1, wherein the protrusion ona plate pair extends to an adjacent plate pair, touches them, and isintegrally connected to the adjacent plate pair.
 11. The heat exchangeras claimed in claim 1, wherein the protrusion is incorporated in theupper plate and the protrusion has an upper plate annular surface whichtouches a lower plate annular surface of the lower plate of an adjacentplate pair and, is integrally connected to the lower plate annularsurface by.
 12. The heat exchanger as claimed in claim 1, wherein aprotrusion is incorporated in the lower plate and the protrusion has alower plate annular surface which touches an upper plate annular surfaceof the upper plate of an adjacent plate pair and is integrally connectedto the upper plate annular surface soldering.
 13. The heat exchanger asclaimed in claim 1, wherein the flow channels are stacked.
 14. The heatexchanger as claimed in claim 1, wherein the cover is placed on thehousing or the housing shells in a stacking direction.
 15. The heatexchanger as claimed in claim 1, wherein the upper plate of a plate pairhas an upper plate rim surface, and the associated lower plate has alower plate rim surface, with the upper plate rim surface correspondingto the lower plate rim surface and being integrally connected.
 16. Theheat exchanger as claimed in claim 1, wherein the longitudinal faces oftwo plate pairs which form a flow channel clasp one another at least inplaces, in particular over the entire plate length, and in that, inparticular, the longitudinal face which touches the housing clasps thelongitudinal face of an adjacent plate, in particular the other plate ofthe respective plate pair.
 17. The heat exchanger as claimed in claim 1,wherein broader faces of two plate pairs which form a flow channel claspone another at least in places, in particular over the entire platewidth.
 18. The heat exchanger as claimed in claim 1, wherein the platepairs have turbulence-generating devices, in particular turbulenceinserts or stamped-in structure elements which are arranged in the flowchannels.
 19. The heat exchanger as claimed in claim 9, wherein theprotrusions are conical.
 20. The heat exchanger as claimed in claim 19,wherein the protrusions are streamlined in the direction of thelongitudinal faces, in particular with an elongated or elliptical crosssection.
 21. The heat exchanger as claimed in claim 1, whereinturbulence-generating devices, comprising turbulence inserts orstructure elements formed from the plate pairs, are arranged betweenflow channels and/or in the channels for the second fluid to passthrough.
 22. The heat exchanger as claimed in claim 1, wherein the platepairs are connected to the housing via their longitudinal-face foldedconnections.
 23. The heat exchanger as claimed in claim 1, wherein theinlet area of the housing is arranged in front of the plate pairs in theflow direction of the second fluid.
 24. The heat exchanger as claimed inclaim 1, wherein the outlet area of the housing is arranged behind theplate pairs in the flow direction of the second fluid.
 25. The heatexchanger as claimed in claim 1, wherein the second fluid can flowaround the plate pairs essentially parallel to their longitudinal faces.26. The heat exchanger as claimed in claim 1, wherein the fold on thelongitudinal face is formed by rims of an upper plate and lower platethat are bent in the same sense, and forms a contact surface for thehousing.
 27. The heat exchanger as claimed in claim 1, wherein the foldon the longitudinal face is formed by rims of an upper plate and lowerplate that are bent in opposite senses, and forms a contact surface forthe housing.
 28. The heat exchanger as claimed in claim 1, wherein theplate pairs have side channels for the first fluid on the longitudinalface in the area of the housing walls.
 29. The heat exchanger as claimedin claim 28, wherein the side channels are in the form of an extensionof the flow cross section of the plate pairs.
 30. The heat exchanger asclaimed in claim 29, wherein the extension has a channel height whichcorresponds essentially to the distance between the plate pairs.
 31. Theheat exchanger as claimed in claim 1, wherein the plate pairs have aflow cross section with a channel width b, and the housing walls areseparated by a distance w, where b<w and material bridges are arrangedbetween the flow cross sections and the housing wall, in particularformed from a lower plate and/or an upper plate.
 32. The heat exchangeras claimed in claim 1, wherein the housing is formed in at least twoparts, and has a housing shell as well as a cover.
 33. The heatexchanger as claimed in claim 1, wherein the inlet area of the housinghas an inlet connecting stub, which is arranged in the housing shell orin the cover.
 34. The heat exchanger as claimed in claim 1, wherein theoutlet area of the housing has an outlet connecting stub, which isarranged in the housing shell or in the cover.
 35. The heat exchanger asclaimed in claim 1, wherein the housing has an inlet connecting stub andan outlet connecting stub for the first fluid.
 36. The heat exchanger asclaimed in claim 1, wherein the inlet and outlet connecting stubs forthe first fluid are arranged in the cover or in the housing shell. 37.The heat exchanger as claimed in claim 1, wherein the inlet and/or theoutlet connecting stubs have longitudinal axes which are at an angle tothe plate pairs.
 38. The heat exchanger as claimed in claim 1, whereinthe heat exchanger has a bypass.
 39. The heat exchanger as claimed inclaim 1, wherein a bypass channel for the second fluid is arrangedwithin the housing and parallel to the plate pairs.
 40. The heatexchanger as claimed in claim 1, wherein a separating wall is arrangedin the inlet area for the second fluid.
 41. The heat exchanger asclaimed in claim 1, wherein a separating wall is arranged in the outletarea for the second fluid.
 42. The heat exchanger as claimed in claim 1,wherein the heat exchanger contains at least one non-return valve, whichis preferably integrated in the housing and is located in the outletarea.
 43. The heat exchanger as claimed in claim 1, wherein the bypasschannel is arranged above or below the plate pairs.
 44. The heatexchanger as claimed in claim 1, wherein the bypass channel is in theform of a bypass tube which can be inserted into the housing.
 45. Theheat exchanger as claimed in claim 1, wherein the bypass channel isthermally insulated from the flow channels and/or from the channels forthe second fluid to pass through.
 46. The heat exchanger as claimed inclaim 1, wherein the bypass channel is essentially arranged at adistance from the flow channels and/or from the channels for the secondfluid to pass through.
 47. The heat exchanger as claimed in claim 1,wherein the bypass channel and/or a flow channel which is adjacent tothe bypass channel and/or the channel for the second fluid to passthrough have or has projections by means of which the flow channels orthe channels for the second fluid to pass through are preferablyessentially separated from the bypass tube.
 48. The heat exchanger asclaimed in claim 1, wherein the bypass channel comprises at least onepartial element which is preferably in the form of an open profile andparticularly advantageously is in the form of a U-profile or half-tube.49. The heat exchanger as claimed in claim 1, wherein the bypass channelcomprises two tube halves.
 50. The heat exchanger as claimed in claim 1,wherein the bypass channel has at least one longitudinal separatingwall.
 51. The heat exchanger as claimed in claim 1, wherein a bypassflap can be integrated in the inlet or outlet area of the housing. 52.The heat exchanger as claimed in claim 1, wherein the inlet area has twoseparate inlet connecting stubs as well as one separating wall.
 53. Theheat exchanger as claimed in claim 1, wherein the plate pairs form apack through which the second fluid flows on two paths.
 54. The heatexchanger as claimed in claim 1, wherein an inlet chamber and an outletchamber are arranged on one side of the plate pack and a deflectionchamber for the second fluid is arranged on the other side of the platepack.
 55. The heat exchanger as claimed in claim 39, wherein the bypassis integrated in the housing.
 56. The heat exchanger as claimed in claim39, wherein the bypass is integrated in the cover.
 57. The heatexchanger as claimed in claim 1, wherein the heat exchanger has at leastone flap.
 58. The heat exchanger as claimed in claim 1, wherein the flapis arranged in the inlet area or in the outlet area.
 59. The heatexchanger as claimed in claim 1, wherein the heat exchanger has at leastone bypass valve.
 60. The heat exchanger as claimed in claim 59, whereinthe bypass valve is integrated in the housing.
 61. The heat exchanger asclaimed in claim 59, wherein the bypass valve is arranged in the inletarea and/or in the outlet area.
 62. The heat exchanger as claimed inclaim 59, wherein the bypass valve is a combination valve.
 63. The heatexchanger as claimed in claim 60, wherein the integrated bypass has aseparating wall which can pivot and by means of which the inletconnecting stub and the outlet connecting stub can be short-circuited.64. The heat exchanger as claimed in claim 1, wherein the first fluid isa liquid coolant, in particular the coolant from the cooling circuit ofan internal combustion engine for a motor vehicle, and the second fluidis fed-back exhaust gas from the internal combustion engine.
 65. Theheat exchanger as claimed in claim 1, wherein the first fluid is air,and the second fluid is fed-back exhaust gas from an internal combustionengine for a motor vehicle.
 66. The heat exchanger as claimed in claim1, wherein the heat exchanger has an oxidation catalytic converter. 67.The heat exchanger as claimed in claim 1, wherein the plate pack ispreceded by the oxidation catalytic converter.
 68. The heat exchanger asclaimed in claim 1, wherein the first fluid is a liquid coolant, inparticular the coolant in the cooling circuit of an internal combustionengine for a motor vehicle, and the second fluid is boost air which canbe supplied to the internal combustion engine.
 69. The heat exchanger asclaimed in claim 1, wherein the first fluid is air and the second fluidis boost air which can be supplied to an internal combustion engine fora motor vehicle.
 70. The use of the heat exchanger as claimed in claim1, comprising an exhaust-gas cooler in an exhaust-gas feedback systemfor an internal combustion engine for a motor vehicle or as a heater forheating the interior of a motor vehicle.
 71. An internal combustionengine for a motor vehicle comprising a heat exchanger as claimed inclaim 1, employed as a boost-air cooler for direct or indirect coolingof boost air for the internal combustion engine.
 72. A motor vehiclecomprising a heat exchanger as claimed in claim 1, employed as an oilcooler for cooling engine oil for an internal combustion engine or forcooling gearbox oil for the motor vehicle by means of a liquid coolant.73. A climate control system for a motor vehicle comprising a heatexchanger as claimed in claim 1, employed as a coolant condenser in acoolant circuit of a climate-control system.
 74. A climate controlsystem for a motor vehicle comprising a heat exchanger as claimed inclaim 1, employed as a coolant exhaust-gas cooler in a coolant circuitof a climate-control system.
 75. A climate control system for a motorvehicle comprising a heat exchanger as claimed in claim 1, employed as acoolant vaporizer in a coolant circuit of the climate-control system.